DE2300512A1 - NEW SILVER CATALYSTS AND THEIR PRODUCTION AND USE - Google Patents

Description

SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ N.V., The Hague, Netherlands

"New silver catalysts as well as their production and their Use "

Priority: January 7, 1972, V.St.A., no.216 3.88

The invention relates to modified Silberka.talysatoren that at Oxidation processes can be used, in particular in processes for the production of ethylene oxide by direct Oxidation of ethylene with molecular oxygen. The invention further relates to processes for the production of the modified ones Silver catalysts and their uses.

It is known that support materials containing silver are used as catalysts for the production of ethylene dioxide by means of a controlled incomplete oxidation of ethylene with molecular oxygen can be used. There are already numerous modifications has been proposed to improve the activity and selectivity of the silver catalysts. These modifications

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refer e.g. to the carrier material used, the process for production, the physical form of the silver the carrier material and the use of certain additives in the catalyst.

From US Pat. No. 2,125,333 it is known that "Small amounts" of alkali metals, such as sodium or potassium and / or their salts, as additives to various silver catalysts can use, which are used for the production of ethylene oxide. Later, however, it was rumored that the influence of the alkali compounds was not very favorable.

For example, U.S. Patent No. 2,238,474 mentions that although sodium hydroxide more or less improves the activity of the silver catalysts, potassium hydroxide does just that produces the opposite effect on catalyst performance. Furthermore, US Pat. No. 2,765,283 described that the addition of 0.0001 to 0.2 percent by weight of an inorganic chlorine compound, e.g. sodium chloride, to the Catalyst support material improves the final catalyst prior to application of the silver. However, in the USA patent 2,799,687 has been disclosed that when 0.002 to 1.6 weight percent inorganic halide such as sodium chloride or preferably Potassium chloride, added as separate solid particles to a fluidized bed of the silver catalyst, the halide has an inhibiting effect on the activity of the catalyst.

From this it can be seen that the addition of alkali metal compounds to a silver catalyst used in the production of

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"■" 5 -

Ethylene oxide is used in one way or another Properties of the silver catalyst changed. However, there are no real advantages with regard to certain amounts to be added Alkali metals; nor any special chemical Advantages over the addition of certain alkali metals other alkali metals.

It has now been found that, surprisingly, the addition of 0.00035 to 0.0Cj50 g-Equiyalente $ e kg of catalyst, based on its total weight, of ions of potassium, rubidium or cesium or their mixtures, if they are carried out simultaneously with the Silver applied to the carrier material of the catalyst four eggs, causing an improved selectivity in the catalyst obtained in this way.

On the other hand, it has been found that the addition of lithium or sodium ions does not cause improved selectivity. Farther it has been found that the addition of greater or lesser amounts of potassium, rubidium and / or cesium is not beneficial is, and further that the addition of the alkali, expressed in g-equivalents, to the carrier material before the application of the Si3-bers brings little or no benefit.

The present invention therefore relates to silver catalysts consisting of silver and at least one alkali metal compound on a porous, heat-resistant carrier material, which is characterized in that the catalysts O, OOOj55 to 0.0030 g equivalents per kg of catalyst (based on the total weight of the

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P! = T ' ^! JMTiG

Iy sa tors) contain potassium, rubidium and / or Carsr'-iyrions., which simultaneously with the silver on the carrier material have been applied.

The catalysts according to the invention consist of an iron ₅ -hitzobesistenton carrier material, on the outer and inner surfaces (pores) 1 '»5 to 20 percent by weight, based on the total weight of the catalyst, silver and certain amounts of potassium, rubidium and / or Caesium ions have been applied. Unless otherwise noted, these three metals are referred to below as alkali metals. Excellent results are obtained with each of these alkali metals. The use of potassium is cost effective, while the use of cesium improves the selectivity the most. Rubidium improves the catalyst more than potassium. Mixtures of alkali metals can also be broken up »

The alkali metals are more likely to be found on the catalysts in Form of the cations than in the form of the extremely active free ones Alkali metals. On the other hand, silver is found on the final catalysts as Meta3.1.

The amount of the alkali metals according to the invention on the catalyst surface is critical. It has been found that amounts below 0.00OJj g-equivalents per kg or above 0.0032 £ - Equivalents per kg do not produce any real improvement. The Al-.

Potash metals are therefore in quantities from 0.06 to 0.50 Equivalents per leg of the finished catalyst. Preferred Men

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genes are in the range from 0.000 ¹ J to 0.0027 g-equivalents per kg. Within this concentration range, minor changes in the concentration range of each of the alkali metals according to the invention can occur, with an optimum selectivity "being obtained if the catalysts containing the alkali metal in question are used in the partial oxidation of ethylene to ethylene oxide. It is therefore advantageous to use the optimum concentration range of To express the alkali metals on the catalyst separately for the individual alkali metals according to the invention, the optimal concentration of the alkali metal range for potassium is about 0.00077 to about 0.0025 g-equivalents per kg of ena catalyst, with amounts of about 0.0010 to about 0.0021 g equivalents per kg of catalyst are most preferred For rubidium, the optimum concentration range is from about 0.0006 to about 0.00 ^ 0 g equivalents per kg of final catalyst, with amounts from about 0.00075 to about 0.0027 g -Equivalents per kg of the final catalyst, most preferably s ind. In the case of cesium, the optimum concentration range is from 0.00035 to about 0.001.9 S equivalents per kg of the final catalyst, amounts of from about 0.0004 to about 0.0017 g equivalents per kg of the final catalyst being particularly preferred.

The concentrations of the applied alkali metals are given below in percent by weight, based on the total catalyst. Thus, potassium and can be OOj55 to 0.0085 percent by weight, preferably from 0.00 to 0.008 percent by weight ¹ I-, in amounts from 0.003 to 0.009 percent by weight, in particular from O,. Rubidium can be used in amounts from 0.0066 to 0.0248 percent by weight,

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in particular from 0.0077 to 0.02 ^ 0 and preferably from 0.0088 up to 0.0232 percent by weight can be used. The amounts of cesium can be from 0.0026 to 0.0252 percent by weight, in particular from 0.0028 to 0.0258 and preferably from 0.005 to 0.0226 percent by weight be.

It must be taken into account that the aforementioned amounts for potassium, rubidium and / or cesium are not necessarily the total amounts of these metals which are present in the catalysts. The amounts of the alkali metals given above relate to those on the surface of the catalyst5 and have been intentionally added to the catalysts, specifically together with the silver. It is therefore not unusual that frequently "is present up to 1 percent by weight of alkali metals, usually potassium in the porous carrier material, depending on its method of _production}. Amounts of alkali metals which are present in the carrier material, rather than being deposited simultaneously with the silver on the surface, not seem to improve the performance of the

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inventive catalysts to contribute and are in the Calculation of alkali metal concentrations generally neglected.

The catalysts according to the invention preferably contain 3 Ms 15 and, particularly advantageously, k to 15 percent by weight of silver as metal, based on the total weight of the catalyst. The use of larger amounts of silver is possible, but generally economically uninteresting. The silver is deposited on the inner and outer surfaces of the carrier material and should be distributed as evenly as possible over the entire surface.

The physical form of what is deposited on the substrate Silver can vary and does not appear to be in accordance with the invention to be critical. Very good results are obtained with a catalyst according to the invention with a controlled alkali metal content obtained on the surface when the silver is in the form of evenly distributed, discontinuous, firmly adhering, " essentially hemispherical discrete parts with a uniform diameter under lyu is present. The best results are obtained with catalysts in which the silver particles have a diameter of 0.1 to 1.5 and an average diameter Have diameters in the range from 0.15 to 0.75 / U.

For that used in the catalysts of the invention Support material can be numerous conventional porous refractory catalyst support materials or commercially available materials

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are used essentially in the presence of the Oxidation of Ethylene Occurring Products and Conditions are inert. Such common materials can be of natural or synthetic origin and preferably have a large-pore structure, i.e. that the structure has a surface

ρ ρ

below 10 m / g and preferably below 2 m / g. These

Carrier materials typically have a measurable porosity of over 20 percent. Very suitable carrier materials are based on silicon and / or aluminum compounds. Examples of such ^; Carrier materials are aluminum oxides, for example the products sold under the trademark "Alundum", charcoal, pumice stone, magnesium oxide, zirconium oxide, diatomite, puller earths, silicon carbide, porous agglomerates of silicon dioxide and / or silicon carbide, selected clays, synthetic · Or natural zeolites, gel-like metal oxides of heavy metals such as molybdenum or ·: VJoIfram, or ceramic materials. The heat-resistant support materials which are particularly advantageous for the production of the catalysts according to the invention consist of aluminum compounds, in particular with a content of oC aluminum oxide. In this case, those are particularly preferred which have a specific surface area of 0.03 to 1.0 m / g according to the BET method (cf. S. Brunauer, PH Emmet and E. Teller in J. Am. Chem. Soc. 60 (19 ^ 8) pages 309 bis; 516), and have a measurable porosity of 25 to 50 percent by volume, the latter having been measured by means of the usual mercury or water adsorption method.

The advantages of the inventive addition of the "special alkali

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metals are especially evident when certain types of <* ■ -aluminium oxide containing carrier materials can be used. These cc-aluminum oxide support materials have a relatively high uniform pore diameter and can be characterized by the following parameters:

(1) The B.E.T. surface area ranges from 0.1 to 0.8 m / g,

preferably 0.35 to 0.6 m "/ gj

(2) the measurable porosities are in the range from 42 to 56, preferably from 46 to 52 percent.

Typical examples of these particularly advantageous aluminum oxide support materials the "Alundum" grades are LA-956, LA-5556 and LA-4118 sold by Norton Company. Further details of these support materials can be found in the following Table I can be seen.

Table I.

Carrier material

LA-956

LA-5556

LA-4118

Surface, m / g

Specific pore volume ,. _cm

Mean pore diameter, / U

Percentage of pores between 1.5 and 15 / U

0.17 0.19

79

0.24

0.25 4.4

81

0.55

0.51

5.7

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Regardless of the type of carrier material used, it is advantageous to shape it into particles, granules, pieces, pellets, rings, spheres and the like of a suitable size for use in fixed bed applications. In the industry standard fixed bed reaction vessels Äthylenoxidations typically consist of a plurality of parallel to each other in a suitable shell arranged long tubes of about 2.5 to 5j1 cm in diameter and 7 to lh m length, which are filled with the catalyst. With these reaction vessels it is advisable to use a carrier material with rounded shapes, such as spheres, pellets, rings or tablets, with a diameter of 2.5 to 20.5 rom.

In summary, it is stated that a catalyst suitable according to the invention consists of 1.5% to 20% by weight of silver, based on the total weight of the catalyst, and of 0.000 ^ 5 to 0.00 ^ 0 g equivalents per kg of catalyst potassium, rubidium and / or cesium, which have been applied evenly distributed together with the silver to the surfaces of a porous, heat-resistant carrier material. A catalyst is more preferred which consists of > to 15 percent by weight silver and from 0.00C40 to 0.0027 g equivalent per kg of catalyst. Potassium, rubidium and / or cesium, which have been applied evenly to inner and outer surfaces of a porous aluminum oxide carrier material with a surface area of 0.03 to 2 m / g. A very preferred catalyst consists of 4 to 15 percent by weight of silver in the form of firmly adhering hemispherical discrete particles with a uniform diameter of less than 1 / rev, which together

ι /

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with 0.0004 to 0.0019 g · equivalents per kg of potassium, rubidium and / or cesium evenly over the inner and outer surfaces of a c <.- Alu]: iinium oxide carrier material with a speslfischen Surface from 0.1 to 0.8 m / g, measured according to the B.E.T. Method that have been applied.

It is clear that the catalyst according to the invention is produced in this way must be that a simultaneous deposition of silver and the desired alkali metal or the alkali metals on the catalyst support surfaces as it has been found that simultaneous deposition with silver is essential for effectiveness the alkali metal additives is critical.

Numerous methods are known for applying silver to carrier materials. The carrier material can e.g. aqueous solution of silver nitrate to be impregnated and dried. Then the silver is mixed with hydrogen or hydrazine reduced as described in US Pat. No. 5,575,888 is. The carrier material can also be impregnated with an ammoniacal silver oxalate or carbonate solution. By Thermal decomposition of the oxalate forms the metallic silver deposit. Furthermore, the carrier material with special aqueous silver salt solutions and mixtures of ammonia, are impregnated with vicinal alkanolamines and vicinal alkyldiamines and then thermally treated, as described in the patent ..... '(Patent application P 21 59 546.4-41) is described. Other possible Processes for applying silver consist in impregnating a carrier material with an ethanolamine-containing one

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Solution of a silver salt and subsequent reduction, as described ■ in Japanese Patent 19 606/1971, or by adding a slurry of finely divided silver carbon? ·, ts on a carrier material and thermal decomposition, as described in US Pat. No. 3Q4J854. In these procedures silver is applied to the carrier material if the carrier material in contact with a liquid phase, either a silver salt solution or a slurry of silver particles is brought. There is an excellent one in these methods Method for adding the desired alkali metals, which allows simultaneous precipitation with silver, in dissolving these alkali metals in the form of suitable salts in the liquid phase in such an amount that the required Amount of alkali metal on the finished catalyst is obtained when the solution is brought into contact with the support material. In general, all alkali metal salts which are soluble in the liquid phase from which the silver is deposited are suitable shall be. In this regard, using common anions with the alkali metal salts does not become unusually effective observed. Examples of such anions are nitrates, Ni-,. trite, chlorides, iodides, bromides, bicarbonates, oxalates, acetates, Tartrates, laetates, isopropoxides and similar common alkali metal salts. One must of course avoid such alkali metal salts as those with the silver present in the liquid phase react, i.e. the silver salts prematurely from an impregnation solution fail. For example, potassium chloride must not be used in impregnation processes where a aqueous silver nitrate solution is used. But it can be

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Manifestly are used in such procedures, which mi L. '■' work an aqueous solution of a silboramine complex, from which SJiberchlorM does not precipitate. _ '"\

■■■ * Gcigoii3tirj.il the invention, is therefore still a precedent for. ■ '<■ "preparation of silver catalysts, wherein a separation of - · ^, silver on the surfaces of porönen, -riit ^ ebeständigen carrier". "V materials takes place, which is characterized in that the _(' 'surfaces of the v !.. support; ·; impregnated terials m ± p a .'Jlösung, ^"are * 'that and a solvent for one to 20 Gevricnt ^ * - ^; prozeiTC J" aussei- yilberubscheidung the TrägormateriPl'' · ■ ^. 'V chenc ¹ «- amount of silver salt asiie one for a 0.0OCJp to 0.0030 £ -' - ^ Squivalento jo kg of Ka t al y r. Ti t or / Aus ο called an Kaljuin-j Rubidiumu The impregnated carrier material contains a sufficient amount of potassium, rubidium and / or carbon ions on the carrier material von eier überc: rc.chü:; 'sigen impregnation solution separated' and then 'send cir-s silver salt xu silver reduced.

Suitable T "apr-ilgnierlÖ £: uiigen contain, for example '*) to ^ O Gewicht.?»- pro.v.ent Si.lbersalk'. and 0.0023 to 0.05 percent by weight of the desired ■ alkali metals or the AllaÖ.irnetv.lle. , *. -

'.' DJE _£: xgcwondetcn genauon concentrations könnon 'in airgemeinen Vorvfi-cuche require, since the deposited from the solution AlkcJ'.lmetallmengej the kritic-.ch ir; ^ t depends in part on the _d.er% PoronltKt used TrMgerm t ^ rials . On the other hand, methods for varying the deposited silver and / or alkali totalinic genes cbciBo are common, such as the analytical determination of the amount of 'der- "-

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actually deposited materials.

The invention also includes a

Optionally applicable and particularly preferred method for the simultaneous deposition of silver and alkali metal or alkali ' lime metals on the carrier surface, which is a simple control measure allowed for the amount of alkali metal deposited within the limits of the present invention, i.e. from 0.00035 up to 0.00 ^ 0 g equivalents per kg of the end catalyst. This method consists in the deposition of a larger than required amount of the deposited simultaneously with the silver Alkali metal according to the general procedure described above, the catalyst particles thus produced with an anhydrous alkanol having 1 to 2 carbon atoms be brought into contact. The alkali metals of the present invention are to a sufficient extent in those described Alkanols soluble, so that one or more washes with the alkanols selectively an excess of the simultaneously co-precipitated Remove the alkali metal so that the amount remaining unchanged on the carrier surface is within the <■ is found in accordance with the critical concentration range. This Process allows easy adjustment of the alkali metal concentration, starting from excess quantities - compared to those as they are described according to the invention, - regardless of whether the Excess was applied intentionally or inadvertently - to the specific concentrations within the range specified by the invention given limits, this process also being used on a larger scale is easily applicable.

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The preferred embodiment described above is explained in more detail below. After a thermal treatment to decompose the silver compound into silver, the catalyst is brought into contact with a lower alkanol having 1 or 2 carbon atoms, ie methanol or ethanol. Mixtures of these can also be used in place of each individual alkanol. Small amounts, such as up to 5 percent by volume, of other substances may be present, for example benzene in denaturing amounts in ethanol. The alkanols to be used are preferably essentially anhydrous; larger amounts of water must be avoided. The temperature used during contact with the alkanol is not critical. The best results are obtained when heated alkanol at about 40 C to the boiling point of the alkanol is used. Higher or lower temperatures are also effective. The amount of alkanol used can vary. In the case of batch treatment, it is generally advantageous to use at least enough alkanol that the catalyst is completely immersed. Even better results are obtained when working in batches if the catalyst is immersed 2 to 4 times and, if possible, 2 times 5 times in fresh alkanol. Each touch typically takes about 5 to 30 minutes, although this time does not appear to be critical. It is obvious, however, that the discontinuous mode of operation described here can easily be transferred to a continuous mode of operation. After it has been brought into contact with alkanol, the catalyst must be separated off from the alkanol. This is generally done by separating the entire batch, such as by sieving or draining the

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Liquid or by drying, such as heating or transferring large quantities of troeknaid gas, such as air, nitrogen, Methane, ethylene or the like, over the catalyst. This However, drying must be carried out completely, since remaining alkanol affects the formation of ethylene oxide very strong.

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£ ■ - ■ '"-

The addition of alkali metals according to the invention is special effective when in conjunction with silver catalyst manufacturing processes in which the silver is applied to the Carrier material from a basic solution, in particular from a Basic Lräur ^ containing nitrogen compounds is applied. Examples of such nitrogen compounds are ammonia and alkylamines. and alkanolamines.

According to a preferred embodiment, the invention is based on the invention Catalysts produced in that

(A) on a porous aluminum-containing support material

J) up to 15 percent by weight of silver in the form of a water-soluble silver salt and 0.00035 to 0.00 ^ 0 g-equivalents per kg of potassium, rubidium and / or cesium in the form of water-soluble salts are applied in that the carrier material with an alkaline aqueous solution of silver and alkali metal salts is brought into contact and that

(B) the product of stage (A) is held at temperatures of 100 to 500 ^° C. in the presence of a reducing agent for a time sufficient to convert essentially all of the silver salts into silver.

In a preferred embodiment, an alumina support material is used impregnated with certain aqueous solutions containing both alkali metal and silver salts. Afterward the silver salt is thermally reduced. The impregnation

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solution contains:

A. a silver salt of a carboxylic acid,

B. a solution that mediates or forms complexes and also serving as a Rediikirionsmltte.l organic An;: Ln,

C. a potassium, rubidium and / or cesiuni salt and

D. an aqueous solvent. '

Examples of suitable silver salts of carboxylic acids to be used and of organic amines which form solvents or form complexes and also serve as reducing agents, as well as of aqueous solvents are described in the patent ..... (patent application P 21 59 ^ -6J- ¹ II).

Alkali metal salts of inorganic and organic carboxylic acids can. . be applied. It is often purposeful. massive., as alkali metal salts salts of such carboxylic acids to use, which are also the basis of the silver salt. For example, ns.n uses potassium, rubidium and / or cesiutrioxalate when Silver oxalate is used as a starting compound for silver.

It has already been pointed out that it is essential that only very specific amounts of the three alkali metals are present. These quantities-can-either by a controlled addition of the Alkaliiiietallsalses or the alkali metal salts to an alkali metal salt-free or an insufficient amount of alkali i-

> cr ^ "'ha_lJ; ends _i _Sil_l ^ e rsalzlöoung / metal salt or AlkalimetalTeäTzerx / öcIer by em controlled removal of alkali metal salt or alkali metal salts from a

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KU much ■ Alkaliir.et :-iXlsal2 or alkali metal; - ^ Xze containing / or from the carrier surface after an application greater than required amounts of alkali metal ?. can be achieved.

For example, a potassium containing

Silberoxalstlcsung can be produced by two processes. Binma-1 can be made with a mixture of ethylenediamine and silver cici Oral acid ULv- ^ Citst v.'orden, v; oh-i mn η a solution with a content on a silver oxalate-a'tliylenediamine complex, to which then a controlled amount of potash and possibly others Amines. ”How ethanolamine is 'added'. Second, can one silver oxalate from a solution of potassium oxalate and silver nitrate precipitate and wash the precipitate repeatedly in order to remove the adhering? Ialitin:? al / ie until the gevaJnsehto Kai ium content is reached. Dar; Potassium containing silver oxalate can then brought into Lömmg with ammonia and / or amines.

Ψ-ζιχη the carrier material with the vw ^ enanrit-en solutions zuB-rt C brought v. ^T iftl, both silver and alkali metal or alkali metals separate at the same time in the form of their corresponding salt

on the treacherous surface? "^ ->.

The impregnated tracer material is then heated to temperatures of 100 "to 57! 3 ⁰ C, before £ u euoise 125 to 525 ° C, a time required for the decomposition of the silver salt, in particular 50 minutes to δ hours, v.-even though a solid deposit of metallic dust particles forms on the surface. Lower temperatures should be avoided, as they do not cause a corresponding "decomposition of the silver salts. Ep, however, different temperature ranges can be used for the decomposition of the silver salts.

ORIGINAL

If necessary, a solution of the silver oxalate-ethylenediamine complex, which contains larger than required amounts of alkali metal, can be used. In this case there is a reduction the alkali metal concentration after decomposition the carrier material and after a subsequent thermal

_v to transfer, treatment to convert the silver compound into metallic silver7 'by bringing the carrier material into contact with a lower alkanol, ie -methanol or ethanol, according to the general procedure described above.

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is i / ^r v f the inventive alkali metal addition in accordance with the most preferred silver deposition method is used, the erha.ltene silver catalyst contains silver in a desirable finely divided uniform particle shape.

The silver catalysts containing alkali metals according to the invention act particularly selectively in the direct oxidation of ethylene with molecular oxygen to ethylene oxide. The conditions to carry out such an oxidation in the 'presence of silver catalysts * according to the invention correspond to broadest sense those already described in the S ^ riä der Technik are. This applies in particular to suitable temperatures, pressures, residence times, diluents such as nitrogen, Carbon dioxide, steam, argon, methane or other saturated hydrocarbons, the presence or absence of damping agents to control the catalytic! Effect, like 1,2-dichloroethane, Vinyl chloride or chlorinated polyphenyl compounds, also the possibility of guiding the reactants in the Circulation or application of subsequent conversions in other reaction vessels to increase the yields of ethylene oxide, as well as other special measures that can be selected in processes for the production of ethylene oxide. In general The pressures in the range from normal pressure to about 55 atm are applied. However, higher pressures are by no means excluded. The molecular one used as the reactant Oxygen can be obtained from common starting compounds, A suitable oxygen charge can essentially consist of relatively pure oxygen, a concentrated acidic

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material flow with a larger amount of oxygen and less Amounts of at least one diluent, such as nitrogen, argon USV /., Or from another oxygen-containing stream, like air. It can therefore be seen that the use of the silver catalysts according to the invention in ethylene oxidation processes is in no way limited to the application of certain conditions from the full range of those as are known to be effective.

In a preferred application of the silver catalysts according to the invention Ethylene oxide is produced by the fact that a Gas obtained from air and containing over 95 percent oxygen with ethylene in the presence of the silver catalysts at one temperature in the range from 210 to 285 ° C, preferably 225 to 270 C, is brought into contact. - - -

Using the silver catalysts according to the invention in Ethylene oxidation processes in which an oxygen-containing gas is mixed with an ethylene-containing gas under ethylene oxidation conditions is contacted, total ethylene oxidative selectivities to ethylene oxide at a given Obtain ethylene conversion that are higher than those selectivities that are getvesen possible with conventional catalysts.

Although'a reason for this with the catalysts according to the invention observed selectivities are not yet fully recognizable, it should be noted that investigations * have shown that Usual silver catalysts that do not contain any alkali metals in the according to the invention contain specified amounts, a decomposition

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300512

of Ä'thylenoxids after its formation 'cause, while the silver catalysts according to the invention, which therefore contain 0.000 ^ 5 to 0.0030 g-equivalents per kg of co-precipitated alkali metals, do not cause any messbs, real ethylene oxide decomposition.

The examples illustrate the invention.

example 1

The catalyst A of the present invention is as follows manufactured. "Alundum", LA-5556, from Norton Company is used as the support material for the catalyst. This Support material consists of rings made of 06 aluminum oxide with a Diameter of 8 mm. This carrier material contains 99 * 3 "percent by weight <* - aluminum oxide, 0.4 percent silicon dioxide and 0.3 per-

cent of other metal oxides and has a surface area of 0.24 m / g and a measurable porosity of 48 to 49 percent by volume. This carrier material has an average pore diameter of

4.4 as determined by mercury porosimetry is. 80 percent of the pores have a diameter in the range of

1.5 to 15 / rev.

The carrier material is impregnated with an aqueous solution of a silver salt that contains a controlled amount of potassium. This solution is prepared as follows: Analytically pure silver oxide is mixed with an aqueous solution of analytically pure oxalic acid which is dissolved in ethylene diamine, forming an approximately 2 molar solution of Ag ₀ (EN) ₉ C ₀ Oi, (EN = ethylene diamine).

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Then 10 percent by volume of kthariolamine (about 0.4 Hol A'th-ano. '! - · am in per mole of silver) is added in order to make the combination which forms the complex and / or serves as a reducing agent. The resulting solution contains about 22 percent by weight silver. Potassium nitrate is then added to the solution so that the solution contains 0.19 percent by weight of potassium. The carrier material is impregnated with the potassium-containing silver solution using reduced pressure in order to achieve complete saturation of the carrier material. Excess liquid is poured off and the support material is immediately placed in a forced air oven at 290 C, dry zn to the catalyst and to reduce the Silbersais to metallic silver. The total battery life is approximately J5 hours. The silver content of the catalyst is determined to be 7 * 8 percent by weight and the potassium content on the catalyst surface to be 0.006 percent by weight (corresponding to 0.0015 g-equivalent potassium e kg catalyst).

The shape of the silver precipitate on the catalyst becomes electron microscopic examined. Discrete particles are found with a uniform diameter of 0.2 to 0.4 / U. These particles are uniform on the inner and outer surfaces of the carrier material arranged. Repeatedly dropping and shaking the catalyst A. reveals that the silver particles stick extremely tenaciously to the substrate surface «

For comparison purposes, the preparation of the aforementioned catalyst repeated, but with the change that no potassium is added to the impregnation solution. Based on the analysis

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230051?

it is determined that there is less than 0.0005 weight percent potassium in the solution. The catalyst "Catalyst A," contains 7 * 8 weight percent silver and has a physical Micro-structure similar to that of catalyst A.

The two catalysts A and, L are comparatively in the Investigation of the production of ethylene oxide. In a typical attempt v / ground 8 mm rings of catalyst A crushed and 3 * 5 pounds from 0.4 to 0.6 mn particles of the crushed catalyst into a reaction vessel with a diameter of 5 ram and given a length of 125 mm. In the presence of a chlorine-containing Moderator (dampening agent) is a mixture of air and ethylene over the catalyst under the following reaction conditions directed:

Pressure 15 ata

Space-time speed 3300 / hour

Ethylene feed to feed 30 mole percent

Ethylene / O ₂ ratio 3 * 75

Moderator concentration 0.001-0.0015 percent by weight of chlorine equivalents.

The reaction temperature is adjusted so that a 52 percent Oxygen conversion is achieved} thereby the selectivity becomes the ethylene oxide formation is determined. When the catalyst A is a temperature of 253 ° C is required to achieve standard oxygen conversion (52 percent). The selectivity on Ethylene oxide is 78 percent. For comparison, the catalytic converter A, only a selectivity of 69 percent.

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Example 2

It becomes the catalyst B using the same as in Example 1 for the catalyst A described method prepared.

The carrier material used as in Example 1 is impregnated with an aqueous solution of potassium and silver salts which has been prepared by the following different process · An aqueous solution of reagent grade silver nitrate is mixed with an aqueous solution of analytically pure potassium oxalate while stirring. The precipitated silver oxalate is filtered off and washed repeatedly with demineralized water until the potassium content is 0.0008 percent by weight potassium per weight per sent Silver amounts. This potassium-containing silver oxalate is then dissolved in aqueous ethylenediamine. With the solution becomes the carrier material impregnated as described in Example 1. The finished catalyst contains 7 * 8 percent by weight silver and 0.00β2 percent by weight at the same time precipitated potassium.

_{For comparison purposes, a catalyst B 1 is} prepared in an analogous manner, with the exception that the number of washes of the silver oxalate is changed. The catalyst contains 0.031 percent by weight of co-precipitated potassium.

If, according to the statements in Example 1, the catalyst

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tor B is used as the ethylene oxidation catalyst, a standard conversion is obtained at 253 ° C, the selectivity of ethylene oxide being 78.6 percent. The catalyst B _1, on the other hand, is inactive as a catalyst for the production of ethylene oxide.

Example 5

Using the starting compounds described in Example 1 and general catalyst preparation processes, a number of silver catalysts with different potassium contents are used which are both within and outside the scope of the present invention. The compositions These catalysts, each 7.8 + 0.3 percent by weight Contain silver are listed in Table II below .

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Table II Weight
percent
potassium Oxidative
selectivity
with ethylene
oxide, 0.0010 '68.5 0.0014 69.4 Kata
lyser Amount of alkali metal added 0.0024 70.6 C. 0.0027 70.4 D. g equivalents
- alkali metal
per kg of kata
lyser 0.0042 74.5 E. 0.00026 0.0044 75.0 F. 0.00057 0.0065 76.5 G 0.00062 0.0064 76.2 H 0.00065 0.0072 76.0 I. .0.0011 0.0082 75.5 J 0.0012 K 0.0016 L " 0.0016 0.0018 0.0021

Each of these catalysts is subjected to a long-term test in an ethylene oxide reaction vessel with a diameter of about 45 mm and a length of 12 m in a semi-technical ± Bn scale and below Subject to test conditions:

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2300512 15.3 ata pressure up to 260 ° C Temperature 245 33OO / hour Space-time speed 30 fo Ethylene feed in the feed Ethylene / 0 _o ratio 52 pounds Oxygen conversion

Moderator optimum concentration from 0.0011 to 0.0014 wt -f o.

Chlorine equivalents

Example 4

Using the starting compounds and the
General procedural rules according to Example 1 produced catalysts which contain different amounts of rubidium as the alkali metal. Instead of adding potassium to the impregnation solution, rubidium is added as rubidium nitrate. The catalysts produced in this way are investigated as ethylene oxide catalysts using the apparatus and the method according to Example 1. The compositions of these catalysts and the
results obtained using these catalysts
the preparation of ethylene oxide are given in Table III below.

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Table ΙΙΓ

ο ο co

Silver - Rubidium content Weight
percent To achieve
a 52 percent Oxidative
selectivity catalyst salary
( Weight-fo) g equivalents
per kilogram 0.0058 term 0p-Umv; and-
required
lich reaction
thermoeratur to ethylene
oxide,
% M. 7.8 0.00068 0.0090 25 ^, 0 73.4 N 7.8 ■ 0.0011 0.0125 257.5 77.5 0 7.8. 0.0015 '0.0155 249.0 79.7 P. 7.8 0.0018 0.0155 258.5 79.0 P ' 7.8 0.0018 0.0179 255.5 79.5 7.8 0.0021 0.0180 263.0 79.9 'R 7.8 0.0021 0.0247 260.0 78.3 S. 7.8 0.0029 0.0273 286.0 74.9 S ' 7.8 0.0032 315.0 67.4 _M.
Ca)
O CD

Example5

Using the starting compounds and the general procedural instructions according to Example 1 produced catalysts containing different amounts of cesium as the alkali metal contain. Instead of adding potassium to the impregnation solution, cesium is added as cesium nitrate. That kind of Catalysts prepared are used as ethylene oxide catalysts using the apparatus and method of Example 1 examined.

The compositions of these catalysts and those using Results obtained with these catalysts in the preparation of ethylene oxide are shown in Table IV below specified.

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Table IV

co ο CO 00 co

O CO cc

catalyst Silver-
'salary
(% By weight ) Cesium content Weight
percent To achieve
a 52 percent
■ term 02-Urawand-
required
lich feedback
temperature, ⁰ C Oxidative
selectivity
to ethylene
oxi d, T 7.8 g equivalents
per kilogram 0.0055 248.5 77.2 U • 7.8 0.00042 Ο, ΟΟδί 256.2 79.4 V 7.8. 0.00061 0.0088 256.0 80.0 W. 7.8 0.00066 0.0090 262.5 79.3 X 7.8 0.00068 0.0095 251.0 79.8 χ ' 7.8 0.00071 0.0094 252.0 ■ 79.8 ' Y 7.8 0.00071 0.0096 . 256.0 80.0 Y ^f 7.8 0.00074 • 0.0097 257.0 80.3 Z '7.8 0.00074 0.0105 252.0 81.0 z ^f 7.8 0.00079 O.OIO5 257.5 80.2 ζ " 7.8 0.00079 0.0105 254.5 79.6 AA ^ 7.8 0.00079 0.0108 247.0 £ 79.5> BB 7.8 0.00081 0.0157 261.5 , _ CO
78.2 0 CC 7.8 0.0012 0.0208 273.5 ^[ ~ ^{} C} - cn DD 7.8 0.0016 0.0265 325.0 65.2 ~ * 0.0020

Example 6 (comparative example)

Using the output method described in Example 1 bonds and general manufacturing processes, two series of catalysts are produced, with one series different amounts of sodium and different in the other series Amounts of lithium are added.

All of these catalysts contain about 7 * 8 percent by weight Silver and 0.005 to 0.152 g-equivalents lithium or sodium per kg of catalyst.

These catalysts are produced using the apparatus and method described in Example 1 investigated as Ä'thylenoxyda.tionskatalysatoren. Within the in the case of the error limits occurring in the tests, no improvement in the selectivity with these catalysts is noticed .

Example? (Comparative example)

According to the procedure described in Example 1, a catalyst is prepared which is at most 0.0005 percent by weight at the same time contains precipitated potassium. The catalyst contains 7 * 8 percent by weight silver. When the catalyst is used as an ethylene oxidation catalyst is examined, he shows a selective

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69 percent efficiency. Samples of this catalyst are treated with aqueous solutions of potassium to add varying amounts of potassium. Even with additions in the range from 0.0009 to 0.0022 g-equivalents per kg of catalyst, a selectivity improvement of at most 4 to 5 percent, ie to a selectivity of 73 to ^r (k percent, is noted.

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Claims (1)

Claims ΐ * Silver catalysts, consisting of silver and at least one alkali metal compound on a porous, heat-resistant carrier material, characterized in that the catalysts O, OOGj55 to 0.00 ^ 0 g-equiva- _t per kg catalyst /
lente / (based on the total weight of the catalyst) contain potassium, rubidium and / or cesium ions that have been applied to the support material at the same time as the silver. 2. Catalyst according to claim 1, characterized in that the catalyst contains potassium. J. Catalyst according to claim 2, characterized in that the amount of potassium is 0.0035 to 0.0085 percent by weight, based on the total weight of the catalyst. 4. Catalyst according to claim J, characterized in that the amount of potassium is 0.004 to 0.008 percent by weight, based on the total weight of the catalyst. 5. Catalyst according to claim 1, characterized in that the catalyst contains rubidium. 6. Catalyst according to claim 5 * characterized in that the rubidium content is 0.0077 to 0.0 240 percent by weight, based on the total weight of the catalyst. 309830/1069 7. Catalyst according to claim 6, characterized in ₉ that the amount of rubidium is 0.0088 to 0.0232 percent by weight, based on the total weight of the catalyst « 8. Catalyst according to claim 1, characterized in that the catalyst contains cesium. 9. -Catalyst according to claim 8, characterized in that the amount of cesium 0, C028 to 0.02 ^ 8 percent by weight, based based on the total weight of the catalyst. 10. Catalyst according to claim 9 *, characterized in that the amount of cesium is 0.00 ^ 0 to 0.0226 percent by weight, based on based on the total weight of the catalyst. 11. A catalyst according to any of the preceding claims, characterized in that the deposited on the refractory support material silver amount 1.5 to 20 percent by weight, in particular 3 to 15 weight percent, preferably H- to 13 weight percent, based on the total weight of the catalyst,. - ■ 12. Catalyst according to one of the preceding claims, characterized in that the silver is in the form of uniform arranged discrete particles with a uniform diameter below 1 / u is present. ^ 13. Catalyst according to claim 12, characterized in that the silver in the form of evenly arranged discrete 30 9 830/1069 230051? Particles with a diameter of 0.1 to 1 / u and an average diameter of 0.15 to 0.75 M is present. lh. Catalyst according to one of the preceding claims, characterized in that the support material is &, -aluminium oxide. 15. Catalyst according to one of the preceding claims, characterized characterized in that the catalyst contains 3 to 15 percent by weight of silver, based on the total weight of the Catalyst, and 0.00C4 to 0.002? g equivalents Potassium, rubidium and / or cesium per kg of catalyst as a precipitate on a porous support material of 06 aluminum oxide with a surface area of 0.03 to 2 m / g contains. 16. Catalyst according to claim 15, characterized in that the catalyst contains 4 to 13 percent by weight of silver, based on the total weight of the catalyst, which is in the form of discrete particles with a uniform diameter of less than 1 / u and which also contains 0, OCtA to Contains 0.0019 g equivalents of potassium, rubidium and / or cesium per kg of catalyst as a deposit on a porous support material made of cc-aluminum oxide with a surface area of 0.1 to 0.8 m ² / g. 17. Catalyst according to claims 15 or l6, characterized in that that the alkali metal is potassium. i
309830/1069 18. Catalyst according to claims 15 or l6, characterized in that that the alkali metal is rubidium. 19. Catalyst according to claim 15 or l6, characterized in that that the alkali metal is cesium. 20. Process for the production of the silver catalysts according to claims 1 to 19 * wherein there is a deposition of silver The surfaces are made of porous, heat-resistant carrier materials, characterized in that the surfaces the carrier material are impregnated with a solution, one solvent and one sufficient for a 1.5-20 percent by weight silver deposition on the carrier material Amount of silver salt as well as one for a 0.00C4 to Deposition amounting to 0.0027 g equivalents per kg of catalyst Potassium, rubidium and / or cesium ions on the carrier material a sufficient amount of at least one potassium, Contains rubidium and / or cesium compound, then the impregnated carrier material from the excess impregnation solution separates and then the silver salt is reduced to silver. 21. The method according to claim 20, characterized in that an impregnation solution is used which is a solvent and one for a J5 to 15 *, preferably 4 to IJ weight percent Silver deposit on the carrier material sufficient amount of silver salt as well as one for a 0.0004 to Deposition amounting to 0.0019 g-equivalents per kg of catalyst Potassium, rubidium and / or cesium ions on the carrier 309 830/1069 230051? material contains a sufficient amount of at least one potassium, rubidium and / or cesium compound, then the impregnated Separates the carrier material from the superfluous impregnation solution and then converts the silver salt to silver reduced. 22. Process for the production of silver catalysts according to claims 1 to 19. » where silver is deposited on the surfaces of porous, heat-resistant carrier materials, characterized in that 1.5 to 20 percent by weight of silver in the form of a silver salt and 0.00C4 to 0.0027 g equivalents each on the porous heat-resistant carrier material kg of catalyst at least one of the alkali metals potassium, rubidium and / or cesium can be deposited in the form of water-soluble salts by bringing this support material into contact with an alkaline aqueous solution of the silver and alkali salts and then the resulting mixture in the presence of a reducing agent to carry out the silver salt is kept at a temperature of 100 to 500 ⁰ C in silver. 23 · The method according to claim 22, characterized in that one on the porous, heat-resistant carrier material at the same time 3 to 15 *, preferably 4 to 13 weight percent Silver, in the form of a silver salt and 0.000 * 1 to 0.0019 g-equivalents ^ e kg of catalyst at least one of the alkali metals Potassium, rubidium and / or cesium in the form of water-soluble salts by bringing this carrier material into contact 309830/1069 HO rait an alkaline aqueous solution r3io; -; t ·· "· silver- um Alkali salts are deposited and then the obtained G ^ .ii ^ h in the presence of a c / s reducing agent to transfer the? Silver balls in silver at a temperature of 100 bio Holds 500 ° C. 24. The method according to claims 22 or 23, characterized in that that you can have an alkaline aqueous lb'sting with a Content of an organic amine used. 25. The method according to claim ? A _} characterized in that ethylenediamine is used as the organic amiri » * Process according to claims 22 or 23, characterized in that a silver salt of a carboxylic acid is used as the silver salt. 27. The method according to any one of claims 20 to 26, characterized in that the amount of potassium. Rubidium and / or cesium, which is incorporated in the silver catalyst, is adjusted by treating the reduced catalyst with an alkanol with one or two carbon atoms « 28. The method according to claim 27, characterized in that: η ·.-Η the alkanol treatment is repeated one or more times, 29. The method according to claims 27 or 28, characterized in that that the alkanol used is essentially anhydrous alkanol. 309830/1069 230051? 30. The method according to any one of claims 27 to 29, characterized in, that the treatment can be carried out at a temperature of about. 40 ° C to the boiling point of the alkanol used performs. 31. The method according to any one of claims 27 to 30, characterized in that that the treatment is carried out for a period of 5 to 30 minutes. 32. The method according to any one of claims 27 to 31 * characterized in that * »Ζ3 one Following this treatment the catalyst is separated from the alkanol or drying the catalyst. 33 · Method according to one of Claims 27 to 32, characterized in that that one treats such a reduced silver catalyst, which by means of a solution of a silver oxalate-ethylenediamine complex, which contains greater than required amounts of potassium, rubidium and / or cesium has been. ~ $ h. A method according to any one of claims 20 to 33, characterized in that the porous heat-resistant carrier material to be impregnated is an et alumina with a Surface area from 0.03 to 2 m / g and preferably from 0.1 to 0.8 m / g, used. 35 · Use of the silver catalysts according to claims 1 to y \ in the process for the production of ethylene oxide by directly 309830/1069 direct oxidation of ethylene with molecular oxygen. 36. Embodiment according to claim 55, characterized in that that a silver catalyst is used, the carrier material of ^ -Aluminium oxide with a surface area of 0.02 to I * 5 m / g and the 3 to I5 weight percent silver and 0.1004 to 0.0019 g-equivalents per kg of catalyst at the same time deposited potassium, rubidium and / or cesium in an even distribution on the outer and inner surfaces contains. 309830/1069 y